1. Field of the Invention
The present invention relates to a method for recording and reading-out a video format signal, and more particularly to a method for recording and reading-out video information and audio information, which take the form of a video format signal, on and from a recording track of a recording medium.
2. Description of Background Information
In the case of recording of audio information corresponding to video information on a recording track of a recording medium along with the corresponding video information, a method is utilized in which the audio information converted to a digital form is inserted in a part of the video format signal while being treated by a time axis compressing process, and the video information is recorded in remaining portions of the video format signal.
As a type of the recording and reading-out method of this sort, the present applicant has already proposed the so-called Still Picture with Sound (SWS) system, which system is described in Japanese Patent application No. 57-186565 filed on Oct. 23, 1982.
In the SWS system, a two-dimensional picture obtained from a video format signal is divided into a plurality of blocks and the audio information is recorded in selected parts of the blocks, and the video information is recorded in the remaining parts of the blocks. Further, a control information which includes information for the control of various playback operations of the playback system, other than the information of the blocks carrying the audio information, is also inserted to the remaining blocks.
By this method, it becomes possible to record the order of playback operations, i.e., a software, on the recording medium itself. Thus, a sequential playback of a series of co-relating picture informations, and audio informations corresponding to the picture informations, is enabled. This sequential playback is quite important for providing various applications of the system such as in the so-called video file system, and in educational "software" or "video soft", etc.
However, in the SWS system, the SWS data are recorded in the frame of each corresponding still picture, which causes an increase of the SWS data portions and a frequent appearance of the SWS data portions (clamped to a constant level) on the screen. In the case of audio information as the SWS data, the same words or phrases are frequently used for the explanations of the still pictures, and in other words, the redundancy is relatively high.
Therefore, it is conceivable to store the frequently used words or phrases in a ROM (read only memory) and read-out those words or phrases from the ROM as needed. However, in the case of this method, a problem occurs in that the quality of the sound is low, and moreover, the ROM has to be changed for each different "video soft".